I have your friend's problem. I have to do sumo deadlifts, instead. I'm getting closer to being able to do conventional ones, but it's taken a lot of stretching to get this loose.
I've concentrated mostly on stretching my hip flexors, but lately, I've found that stretching my glutes has helped, as well.
Part of the ability to get into that position is knowing that you can. I assume the DL position several times throughout the day (to stay loose, but also practice balancing in that position).
Here's an article that I read that has helped me.
Deadlift Diagnosis